NGC185, first time guiding

[wimvb]

NGC 185 is a dwarf galaxy belonging to the Andromeda galaxy (M31). It is magnitude 10.1

By no means a good image, but I'm quite satisfied with the outcome anyway.

 

AZ EQ6-GT with SW 150PDS

Pentax K20D (unmodded, but that's irrelevant for this image) @ ISO 800, Baader coma corrector, Baader UHC lp filter

10 x 15 minutes light frames, 80 bias, old flats, no darks

Guiding: SW ST80 with ZWO ASI120MM and Lin_guider on Raspberry Pi

Due to frost I lost about half my subs; the improvised dew heater couldn't cope with sub zero temperatures.

My camera can't connect to a computer anymore, so I have no possibility yet to dither. Darks would have decreased the hot pixels somewhat, but in my experience not enough to be bothered for this test.

The walking noise suggests that the rig wasn't properly balanced. But I managed to double my exposure time from unguided, with only a few subs being discarded because of star trails(not counting the guidescope freezing over). At this ISO setting, I'm at the limit for single sub exposure time. All in all I'm pleased with the results.

 

Cheers,

[D4N]

It's a great feeling when you get guiding to work

 

You can dither, you will just have to do it manually between exposures.  If you are monitoring the setup you can dither when you hear the shutter close and make sure you have sufficient time delay for it to settle before the next exposure.  I used to find dithering far more effective than darks for removing DSLR noise.

 

I had to make up dew heaters myself to deal with the cold, it can be really bad if you assemble your gear in the nice warm house then take it out as any moisture inside just turns into ice.

[gorann]

Looks promising Wim!

Here is the site that got me building my own dew heaters:

http://www.deepskywatch.com/Articles/newtonian-dew-heater.html

Materials cost almost nothing. In Sweden you can buy the resistance wire (motståndstråd, I use the one with 5.65 ohm/meter) from www.conrad.se (44 SEK for 10 m) and the duct tape from Biltema. If you run it on 12 V you get the regulator from e-bay, like this one:

http://www.ebay.com/itm/DC-12V-8A-LED-Light-Protect-Strip-Dimmer-Adjustable-Brightness-Controller-New-J-/381801800224?hash=item58e5292220:g:pSEAAOSwOyJX9j87

However, I found that if I get the length of the wire about right I may not need to regulate it - just run straight off 12V.

 

 

[D4N]

That's the same PWM dimmer as I use on my main imaging setup.

I have a second ultra portable setup that runs off a 5V USB power bank that I built a 5V dew heater for and just run that with no controller.

[wimvb]

Thanks for the replies. Just made a dew heater this afternoon, but it runs a little too hot from 12 V. Have a 6 v battery, but may get a dimmer for 12v. The cheap dimmers you refer to Göran, are not available through normal channels in Sweden, it seems. Maybe they're not CE certified.

Dan, I have dithered manually last winter. Babysitting my camera in -20 C is something I try to avoid (not there yet, but is very likely in january/february). That was the main reason I made my ditherbox.

Dithering is possible from lin_guider, so I'll check if I can control my camera from the raspberry pi's gpio pins. I will have some time for tinkering, the first possibility for ap will be wednesday night according to the "clear outside" app.

Long term solution: invest in a new camera. I wonder if I should put this on my Xmas wishlist ...

[D4N]

You certainly can get those in Sweden, that's where I got mine

PWM dimmer

 

Your camera is supported by gphoto so you could control it with your RPi that way, you should even be able to use it with ekos/kstars although the controls can be a bit hit and miss with photo support.

If it is a RPi 3 you can install Ubuntu mate and ekos directly onto the RPi, I have them running on mine.  You can then control the RPi using no machine or vnc from the comfort of somewhere warm.

Alternatively you can just use gphoto from terminal if you don't want to install Ubuntu mate and ekos.

[gorann]

Wim, you can easily get those dimmers sent to Sweden. I am the proof of that and I ordered 5 of them. Just order them and CE certification is, as I understood it, for 240 volts, so with 12 Volts (that cannot kill you) you can buy and use anything.

[wimvb]

Thanks for the site. will look into it.

The reason I can't connect my camera to a computer is that the usb port doesn't work anymore. Not even as a storage device. This means I can only connect to my remote control input. I will have to figure out how to control from raspberry pi gpio pins to opto-isolator to camera remote input. Just one more diy gadget to put together.

[wimvb]

7 minutes ago, gorann said:

Wim, you can easily get those dimmers sent to Sweden. I am the proof of that and I ordered 5 of them. Just order them and CE certification is, as I understood it, for 240 volts, so with 12 Volts (that cannot kill you) you can buy and use anything.

I saw them on the chinese site mintinthebox.com. shipping costs tends to be high, and delivery uncertain, from what I've read online. The price on the site that Dan linked to is approximately £ 25 including shipping, for one unit. But I will check the ebay link.

Thanks

[wimvb]

Just found and bought one from a swedish site. More expensive than ebay, but probably also more secure than "sunshine*1023".

They offered invoice payment free of charge, 14 day net (Göran: genom Klarna).

[D4N]

Ah if the camera has a duff USB port then I guess building a RPi controlled bulb would probably be easier than repairing the port.

That actually sounds like a nice project.

 

Yeh delivery from RS isn't cheap as most of their stuff is shipped from the UK, it is very fast though and I have often had things next day from them as they send by DHL rather than PostNord.

[gorann]

Good luck with the heaters Wim! I have bought a lot of stuff like that through e-bay from Chinese sites (particularly Hong Kong) using PayPal, which is secure enough I think.

[PatrickGilliland]

All sounds very technical to me Wim  glad you have some progress though

Paddy

[wimvb]

Thanks, Göran, Dan, and Paddy.

Paddy, it's all very technical for me as well. One reason I put off guiding, is that it is one more thing that can go wrong and takes time from collecting data. Otoh, with guiding, data should be better.

Anyway, the dimmer has been dispatched from the supplier, and maybe wednesday or thursday the skies will clear. at least according to the "clear outside" app

Cheers,

[wimvb]

One homemade dew heater, ready for service.

The box contains 2 12 V lead batteries. The left battery is connected to the dimmer for my guide scope dew heater (attached). The other battery is not dimmed and can power the dew heater for the secondary mirror (is lower power and doesn't need regulating). The dew heater itself is made from NiCr wire, 4 strands wide, and fits my ST80.

[D4N]

Nice, I wrapped the exposed dimmer terminals in self amalg' on mine as it isn't really designed to be outdoors.

[D4N]

On 27/11/2016 at 01:14, wimvb said:

Just found and bought one from a swedish site. More expensive than ebay, but probably also more secure than "sunshine*1023".

They offered invoice payment free of charge, 14 day net (Göran: genom Klarna).

Where did you get it from in the end?  I'm planning to build another heater soon so if there is a cheaper source in Sweden I'll get it from there instead of RS.

[wimvb]

It didn't turn out cheaper, just more secure re payment and shipping.

Http://elkatalogen.se

Since they use Klarna for payment, and have fast shipping through dhl, I considered it more secure than ebay. Since items on ebay can be shipped from anywhere in the world, they may get stuck in customs and cost extra. Your source may be a good alternative.